It is a recent trend in color light-sensitive material that a two-equivalent coupler, in which an appropriate substituent is introduced at the coupling position or reactive position at which the coupler is reacted with the oxidation product of a color developing agent so that one molecular of dye can be formed from the coupler by the reduction of two silver atoms, is used in place of a 4-equivalent coupler by which requires reduction of 4 silver atoms to form one molecule of dye.
Requirements to the coupler are increasingly made harder accompanied with progress in the color light-sensitive material and more improvements are required not only in the color-forming efficiency but also in a color reproducibility, a storage ability of image, a solubility in a high-boiling solvent and a stability of dispersion thereof.
As a technique for improving the color reproducibility and the color-forming efficiency, a yellow coupler has been known, which has a heterocyclic ring having a cyclic imide structure as a releasing group, and an alkoxy group at 2-position of the anilide moiety of the coupler. For example, Japanese Patent Publication Open for Public Inspection (JP O.P.I.) No. 63-38932 describes a yellow coupler having an alkoxy group at 2-position of the anilide moiety thereof and a hydantoin group or a imidazolone group as a releasing group thereof. However, such the coupler has a drawback that the coupler is inferior in the color reproducibility and the light-fastness since a sulfamoyl group is exist as a ballast group.
A yellow coupler improved in the light-fastness while maintaining a high color reproducibility and color-forming efficiency such as one described in JP O.P.I. No. 63-123047 has been known, which has an alkoxy group at 2-position and an acylamino group at 5-position of the anilide moiety. However, such the coupler is inferior in a solubility in a low-boiling solvent such as ethyl acetate and a high-boiling solvent such as dibutyl phthalate. Accordingly, a problem inconvenient to production of color light-sensitive material that a large amount of the solvent is necessary to disperse the coupler is raised. Furthermore, the coupler has a drawback that the coupler tends to be precipitated after dissolved in the solvent. It has been found that such the drawbacks become a impediment to the practical use of the coupler since the drawback are considerably emphasized under a condition for reducing the layer thickness, which is strongly required in recent years. Furthermore, the coupler described in this document is characterized in that a sulfonyl group is included in the ballast group thereof. For introducing the sulfonyl group, a complex synthesis procedure is required and the production cost is made higher.
U.S. Pat. No. 4,338,403 describes a yellow coupler having an alkoxy group at 2-position and a sulfonylamino group at 5-position of the anilide moiety and an imidazolyl group as a releasing group. Although such the coupler has a sufficient light-fastness and stability of dispersion, the coupler is required further improvement in the color-forming efficiency which is the most important property of color-forming coupler.
In European Patent No. 416684, a yellow is described which has an alkoxy group at 2-position and a sulfonylamino group at 5-position of the anilide moiety and an aryloxy group as the releasing group. Such the coupler has a high color-forming efficiency caused by the presence of the aryloxy group, However, the presence of the aryloxy group causes lowering in the light-fastness of the coupler and the lowered light-fastness makes a large impediment to the practical use of the coupler particularly in a color photographic paper.